1. Field of the Invention
The invention relates to a device and a method for manufacturing a foundation for a mass located at height, such as the jacket of a wind turbine or a jetty, wherein the foundation comprises a quantity of piles driven into an underwater bottom in a geometric pattern. The invention also relates to an assembly of a jack-up platform and a device coupled thereto with which the method can be performed.
2. Description of the Prior Art
The invention will be elucidated hereinbelow with reference to an offshore wind turbine. The reference to a wind turbine in no way implies that the invention is limited to the use in the context of such a wind turbine. The positioning framework and the method can likewise be applied on any other structure, such as jetties, radar and other towers, platforms and the like. The support structure of a wind turbine normally has a slender design, for instance in the form of a tube or pillar. This pillar structure has to be coupled to a foundation in the ground. For offshore wind turbines, which are placed in relatively shallow water, it is possible to make use of one mast extending from the machinery housing of the wind turbine to the foundation. In addition to such a mono-pole construction, the support structure of an offshore wind turbine can also comprise a tubular upper part and a lower part in the form of a lattice structure, also referred to as a jacket. A large part of the jacket extends underwater, where the jacket finds support on an underwater bottom, in many cases the underwater bottom. Another option is a support structure in the form of a tripod.
A known method for providing a foundation for a mass located at height, such as the jacket of a wind turbine, comprises of providing an offshore platform in the vicinity of the location provided for the foundation, determining the location for each pile, subsequently manipulating each pile using a lifting crane present on the platform and driving each pile into the underwater bottom. Once all the piles have been arranged in the underwater bottom in the desired geometric pattern, thus forming the foundation, the jacket is arranged on the foundation formed by the quantity of piles by arranging legs of the jacket in the piles (also referred to as pin piling) or, in an alternative method, around the piles (also referred to as sleeve piling). The piles are adapted in both cases to be able to receive the legs of the jacket, for instance by providing hollow piles (pin piling) or hollow legs of the jacket (sleeve piling).
It will be apparent that it is of the greatest importance to not only urge the piles into the ground at the correct positions (the horizontal distance between the foundation piles must thus preferably be accurate to several centimeters), but also to ensure that the piles are arranged substantially at a perpendicular angle in the underwater bottom. In view of the large dimensions of structures such as wind turbines, it is only possible in many cases to allow a maximum variation of 1° relative to the vertical direction.
The invention has for its object to provide a device and method for providing a foundation as elucidated above with a greater accuracy than with the known device and method.